Near-eye three-dimensional (3D) displays have seen rapid growth and held great promise in a variety of applications, such as gaming, film viewing, and professional scene simulations. Currently, most near-eye three-dimensional displays are based on computer stereoscopy, which presents two images with parallax in front of the viewer's eyes. Stimulated by binocular disparity cues, the viewer's brain then creates an impression of the three-dimensional structure of the portrayed scene. However, these stereoscopic displays suffer from a major drawback of a vergence-accommodation conflict, which reduces the viewer's ability to fuse the binocular stimuli while causing discomfort and fatigue. The vergence-accommodation conflict can be attributed to the images being displayed on one surface and the focus cues specifying the depth of the display screen (i.e., accommodation distance) rather than the depths of the depicted scenes (i.e., vergence distance). This is opposite to the viewer's perception in the real world where these two distances are always the same. To alleviate this problem, one must present correct focus cues that are consistent with binocular stereopsis.
Currently, only a few approaches can attempt to provide correct or nearly correct focus cues for the depicted scene, such as light field near-eye displays and multiplane near-eye displays. The light field display employs a lenslet array to project multi-view images simultaneously onto the viewer's retina, thereby yielding a continuous three-dimensional sensation. Despite a compact form factor, the spatial resolution is low (˜100×100 pixels), restricted by the number of pixels that can fit into the imaging area of a lenslet.
By contrast, the multiplane display projects two-dimensional images onto a variety of depth planes through either temporal multiplexing or spatial multiplexing. By synchronizing a fast display with a deformable mirror or a focal sweeping lens, the temporal-multiplexing-based methods project depth images in sequence. However, to render continuous motion, the device must display all depth images within the flicker fusion time ( 1/60 s), thus introducing a severe trade-off between the image dynamic range and the number of depth planes. For example, given 23 k pattern refresh rate at digital micromirror device and six displayed image planes, the dynamic range of each image for this process can be approximately only 6 bits (64 grey levels). Alternatively, the spatial-multiplexing-based methods deploy multiple screens at various distances from the viewer, followed by optically combining their images using a beam splitter. Because of the usage of multiple screens, such devices are normally bulky, making them unsuitable for wearable devices.
While the present disclosure is susceptible to various modifications and alternative forms, exemplary embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description of exemplary embodiments is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure as defined by the embodiments above and the claims below. Reference should therefore be made to the embodiments above and claims below for interpreting the scope of the disclosure.